Topical germicides often contain harsh chemical components which can adversely affect the quality of the skin. The resulting irritation is exacerbated by the presence of materials, such as surface active agents and the germicides themselves, which can disrupt and even dissolve protective skin lipids. The disruption of the lipid barrier of the skin leads to moisture loss and subsequent irritation and cracking. Skin is particularly susceptible to damage under adverse ambient conditions, such as occurs in windy, wet and cold weather, when chapping most often occurs. Irritated, chapped and cracked skin tissue can readily harbor pathogenic bacteria, including those that cause mammalian mastitis. Sore mammalian teats are particularly sensitive to the attachment of the milking claws, which often limits the ability of dairymen to milk the affected quarter.
To reduce the potential for chapping, cracking and related skin irritations, many topical disinfectants, including most current teat dips, include humectants. Humectants are agents that control the moisture exchange between the applied skin and the environment. Typical humectants that are used in teat dips are glycerin and sorbitol, and which contain multiple hydroxyl groups ("polyols"). Such humectants attract water, and when present on skin maintain a higher-than-normal level of moisture. Furthermore, teat tips may also contain relatively higher levels of polyols, such as propylene glycol, to serve as antifreeze agents. Polyols, at their ordinary levels of use in teat dips, of up to about 10% of the disinfecting composition, are relatively inert with respect to other teat dip components, tending to esterify with organic acid germicides at low, and acceptable rates. However, as polyol levels increase, the esterification tendency escalates markedly. The ester formation involves the primary alcohol (i.e., --CH.sub.2 OH) of the polyol.
This tendency to esterify is particularly burdensome when preparing teat dip concentrates, which products are finding increased utility and economy in modern dairy farms. Teat dip concentrates require less bulk shipping and handling, and occupy less space in dairy barns and milking parlors. They are combined with water on site, often by means of equipment which dilutes and sprays the dip in a single operation. Dip concentrates containing germicidal organic acids at levels up to about 20%, are particularly susceptible to such esterification reactions, leading to the reduction of both germicidal and humectant functionality.
A particular area in which polyol esterification is a source of difficulty is in the two-part chlorous acid germicides, wherein an acidified chlorous acid disinfectant is generally formed by combining an activator containing an organic acid with a base containing a metal chlorite. In these two-part systems, the polyol must be combined with the organic acid in the activator because of its instability in the base. A critical aspect of chlorous acid germicides is the need to maintain their pH values in a range where the chlorous acid/chlorite ratio is below about 0.18, so that excessive degradation to chlorine dioxide does not occur. This generally requires the presence of an organic acid buffering system, comprising an acid in pK range of about 2.8 to about 4.2. Concentrates of these two-part organic acid/chlorite systems which also contain polyols in the acid phase are even more difficult to maintain in stable form.
Accordingly, there is a need in the art for improved two-part systems which can stably maintain alcohol-containing humectants or antifreezes with germicidal organic acids, or acid activators for chlorite systems, over an extended period of time. This invention fulfills this need, and provides further related advantages.